Joining method and semiconductor device manufacturing method

ABSTRACT

A joining method that allows joining processing to be carried out simultaneously at a plurality of portions without being influenced by a supply time restriction on a joining material, and a semiconductor device manufacturing method using the joining method are provided. A chip and a lead frame are tentatively assembled having a solid solder block interposed therebetween. The solder block is provided with protruding parts that protrude in one direction. The protruding parts are inserted into solder supply ports of the lead frame, whereby the chip and the lead frame are tentatively assembled. Subsequently, the chip and the lead frame are fed into a reflow oven, and the solder block is melted and thereafter solidified. Thus, the chip and the lead frame are joined to each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 13/655,875,filed Oct. 19, 2012, which claims priority to Japanese patentapplication nos. 2011-257090 filed Nov. 25, 2011 and 2012-183833 filedAug. 23, 2012, the entire contents of each of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a joining method for joining twojoining target members, e.g., a lead frame and a chip of a semiconductordevice, with solder or the like, and to a semiconductor devicemanufacturing method using the same.

2. Description of the Background Art

Two joining target members, e.g., a lead frame and a semiconductor chip(which hereinafter may simply be referred to as the “chip”) of asemiconductor device are joined to each other with a joining materialsuch as solder. According to joining methods of conventional techniques,a heat spreader on which a lead frame and a chip are mounted istentatively assembled before being put into an oven, and molten solderis supplied from a solder supply source in the oven. By solidifying thesupplied molten solder, the lead frame and the chip are joined to eachother (for example, see Japanese Patent Application Laid-Open No.2008-182074).

According to the joining methods of the conventional techniques such asdisclosed in Japanese Patent Application Laid-Open No. 2008-182074,since the solder supply source supplying the solder is provided one innumber, the solder cannot be supplied to a plurality of portions atonce. In the case where the solder is supplied to a plurality ofportions, the molten solder must be supplied to those portions one byone in order, and hence it takes time.

Further, since the heat must be retained while the molten solder issupplied, the base material of the chip may be influenced by the moltensolder at the portions where the molten solder has already beensupplied. For the purpose of suppressing the influence, the heating timeand the processing speed in the joining processing are restricted.Therefore, the time from when the supply of solder is started in theoven until when the supply ends is restricted. This is referred to asthe supply time restriction. The supply time restriction poses a problemthat the number of chips mounted on a semiconductor device cannot beincreased.

SUMMARY OF THE INVENTION

The present invention is directed to provide a joining method that makesit possible to carry out joining processing simultaneously at aplurality of portions without the influence of the supply timerestriction on the joining material and a semiconductor devicemanufacturing method using the same.

A joining method of the present invention includes an arranging step anda joining step. In the arranging step, a solid joining material isarranged between two joining target members. In the joining step, by thejoining material being molten and thereafter solidified, the two joiningtarget members are joined to each other.

According to the joining method, the joining processing can be carriedout simultaneously at a plurality of portions without the influence ofthe supply time restriction on the joining material.

A joining method of the present invention includes a tentativelyassembling step and a joining step. In the tentatively assembling step,two joining target members are tentatively assembled to oppose to eachother with an interval. In the joining step, by a molten joiningmaterial being supplied by supplying means into a space formed by thetwo joining target members, and thereafter solidified, the two joiningtarget members are joined to each other. The supplying means isstructured to be capable of supplying the joining materialsimultaneously to a plurality of portions.

According to the joining method, the joining processing can be carriedout simultaneously at a plurality of portions without the influence ofthe supply time restriction on the joining material.

A semiconductor device manufacturing method of the present inventionincludes a step of joining, using the joining method of the presentinvention, a semiconductor chip having a semiconductor element and alead frame having a lead wire connected to a semiconductor element toeach other, the semiconductor chip and the lead frame being the twojoining target members.

According to the semiconductor device manufacturing method, using thejoining method which, as described above, makes it possible to carry outthe joining processing simultaneously at a plurality of portions withoutthe influence of the supply time restriction on the joining material,the semiconductor chip and the lead frame are joined to each other.Accordingly, the number of pieces of the semiconductor chip mounted onthe semiconductor device can be increased.

These and other objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a first preferredembodiment of the present invention;

FIG. 2 is a plan view showing the structure in a tentatively assembledstate in the joining method according to the first preferred embodimentof the present invention;

FIG. 3 is a flowchart showing the processing procedure in the joiningmethod according to the first preferred embodiment of the presentinvention;

FIG. 4 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a second preferredembodiment of the present invention;

FIG. 5 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a third preferredembodiment of the present invention;

FIG. 6 is a flowchart showing the processing procedure in the joiningmethod according to the third preferred embodiment of the presentinvention;

FIG. 7 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a modification of thethird preferred embodiment of the present invention;

FIG. 8 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a fourth preferredembodiment of the present invention;

FIG. 9 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a fifth preferredembodiment of the present invention;

FIG. 10 is a flowchart showing the processing procedure in the joiningmethod according to the fifth preferred embodiment of the presentinvention;

FIG. 11 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a modification of thefifth preferred embodiment of the present invention;

FIG. 12 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a sixth preferredembodiment of the present invention;

FIG. 13 is a plan view showing the structure in a tentatively assembledstate in the joining method according to the sixth preferred embodimentof the present invention;

FIG. 14 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a seventh preferredembodiment of the present invention;

FIG. 15 is a flowchart showing the processing procedure in the joiningmethod according to the seventh preferred embodiment of the presentinvention;

FIG. 16 is a cross-sectional view showing the structure in a soldersupplying state in a reflow oven in a joining method according to aneighth preferred embodiment of the present invention;

FIG. 17 is a flowchart showing the processing procedure in the joiningmethod according to the eighth preferred embodiment of the presentinvention;

FIG. 18 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a ninth preferredembodiment of the present invention;

FIG. 19 is a cross-sectional view showing other example in a tentativelyassembled state in a joining method according to a modification of theninth preferred embodiment of the present invention; and

FIG. 20 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a tenth preferredembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Preferred Embodiment

FIG. 1 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a first preferredembodiment of the present invention. FIG. 2 is a plan view showing thestructure in a tentatively assembled state in the joining methodaccording to the first preferred embodiment of the present invention.FIG. 1 is a cross-sectional view taken along cross-sectional line S1-S1in FIG. 2. For the sake of easier understanding, a heat spreader 2 and adedicated jig 3 are not shown in FIG. 2.

In the tentatively assembled state, the heat spreader 2 to which asemiconductor chip (which hereinafter may simply be referred to as the“chip”) 1 is soldered is assembled into the dedicated jig 3. The chip 1is plate-like. The chip 1 has its surface on one side in the thicknessdirection soldered to the heat spreader 2. On the chip 1, that is, onthe other side in the thickness direction of the chip 1, a lead frame 5is arranged via a solder block 4. The lead frame 5 is supported bynot-shown supporting means, e.g., a robot arm or a fixing member.

The lead frame 5 is provided with solder supply ports 21. In the presentpreferred embodiment, two solder supply ports 21 are formed. One slit 22is formed between the two solder supply ports 21. The lead frame 5 isplate-like, and the solder supply ports 21 and the slit 22 penetrate thelead frame 5 in the thickness direction. The solder supply ports 21 andthe slit 22 are each formed to be oval as seen from the other side inthe thickness direction of the lead frame 5.

The solder block 4 is made of solid solder. In the present preferredembodiment, the solder block 4 is in a rectangular parallelepiped shape.At the top of the solder block 4, that is, on the surface on the otherside in the thickness direction which is the side in contact with thelead frame 5, protruding parts 11 are formed. The protruding parts 11are formed at the position corresponding to the solder supply ports 21of the lead frame 5. The protruding parts 11 are formed as many as thesolder supply ports 21 of the lead frame 5. In the present preferredembodiment, two protruding parts 11 are formed.

The protruding parts 11 are formed to have the same shape as seen fromthe other side in the thickness direction as the solder supply ports 21of the lead frame 5. In the present preferred embodiment, the protrudingparts 11 are each formed to be oval as seen from the other side in thethickness direction. The protruding parts 11 are inserted into therespective corresponding solder supply ports 21 of the lead frame 5.

FIG. 3 is a flowchart showing the processing procedure in the joiningmethod according to the first preferred embodiment of the presentinvention. When materials and tools used in the joining method accordingto the present preferred embodiment, such as the chip 1, the heatspreader 2, the dedicated jig 3, the solder block 4, the lead frame 5and the like shown in FIG. 1, are prepared, the processing starts andproceeds to Step a1.

In Step a1, after the chip 1 is soldered to the heat spreader 2, theheat spreader 2 to which the chip 1 is soldered is assembled into thededicated jig 3.

In Step a2, the solder block 4 is placed on the chip 1. The solder block4 is placed on the chip 1 such that the surface opposite to the surfacewhere the protruding parts 11 are formed is brought into contact withthe chip 1. In this manner, the solder block 4 is supplied to the chip1. The solder block 4 is previously formed by re-melting using a mask ora mold.

In Step a3, the lead frame 5 is placed such that the protruding parts 11of the solder block 4 are inserted into the solder supply ports 21,whereby the chip 1 and the lead frame 5 are tentatively assembled. Thestep of Step a3 corresponds to the tentatively assembling step.

After the tentative assembly is completed, in Step a4, the tentativelyassembled chip 1 and lead frame 5 are fed in a reflow oven to carry outsoldering. Since the inside of the reflow oven is heated, by placing thetentatively assembled chip 1 and lead frame 5 in the reflow oven, thesolder block 4 is heated and melt. Thereafter, the tentatively assembledchip 1 and lead frame 5 are taken out from the reflow oven and cooled,so that the molten solder block 4 solidifies. Thus, the chip 1 and thelead frame 5 are joined to each other. The step of Step a4 correspondsto the joining step.

As described above, in the present preferred embodiment, the protrudingparts 11 of the solder block 4 placed on the chip 1 are inserted intothe solder supply ports 21 of the lead frame 5, whereby the chip 1 andthe lead frame 5 are tentatively assembled. Thus, the protruding parts11 of the solder block 4 inserted into the solder supply ports 21achieve alignment. Therefore, even when the tentatively assembled chip 1and the lead frame 5 vibrate when being conveyed inside the reflow oven,the solder block 4 will not displace. Accordingly, the chip 1 and thelead frame 5 are stably joined to each other. That is, the chip 1 andthe lead frame 5 can accurately be joined to each other at a pluralityof portions.

Further, in the present preferred embodiment, before the chip 1 and thelead frame 5 are fed into the reflow oven, solder as the solder block 4is supplied between the chip 1 and the lead frame 5. Therefore, withoutbeing influenced by the supply time restriction on the solder in thereflow oven, the joining processing can simultaneously be carried out ata plurality of portions.

Still further, in the present preferred embodiment, since the solderblock 4 being the solid solder is used, variations in the supply amountof the solder can be suppressed to the minimum extent.

Still further, in the present preferred embodiment, the slit 22 isformed between the two solder supply ports 21 of the lead frame 5. Thus,when the solder block 4 is heated in the reflow oven to be re-molten,the solder being molten (which hereinafter may be referred to as the“molten solder”) can take a fillet shape which spreads in a bell-shapemanner from each solder supply port 21 as an apex toward the chip 1side, and whose cross-sectional shape has tapered portions.

Accordingly, since the thermal stress at the portion joined by solder(which hereinafter may be referred to as the “solder-joined portion”)can be relaxed, it becomes possible to prevent the solder-joined portionand the chip 1 from being damaged by the thermal stress occurring uponoperation of the semiconductor device, and to extend the lifetime of thesemiconductor device.

The shape of the solder block 4 is not limited to a rectangularparallelepiped shape, and any shape that includes the protruding parts11 may suffice. For example, it may be in various shapes such as aquadrangular pyramid shape, a spherical shape or the like. Use of thesolder block 4 in such shapes can similarly achieve the effect of thepresent preferred embodiment.

Second Preferred Embodiment

FIG. 4 is a cross-sectional view that shows the structure in atentatively assembled state in a joining method according to a secondpreferred embodiment of the present invention. Since the structure inthe tentatively assembled state according to the present preferredembodiment is similar to the structure in the tentatively assembledstate according to the first preferred embodiment described above, adescription will be given of the different parts, and the correspondingparts are denoted by identical reference symbols and the commondescription will not be repeated.

In the present preferred embodiment, in place of the solder block 4according to the first preferred embodiment, a plate solder 31 is used.The plate solder 31 is made of a plate-shaped solid solder. The platesolder 31 is placed on the chip 1 such that the surface on one side inthe thickness direction is brought into contact with the chip 1. Theplate solder 31 is provided with protruding parts 32 on the oppositesurface which is brought into contact with the chip 1, that is, on thesurface that is on the other side in the thickness direction and that isthe side brought into contact with the lead frame 5.

The protruding parts 32 of the plate solder 31 are formed, similarly tothe protruding parts 11 of the solder block 4 in the first preferredembodiment, two in number in total, at the positions corresponding tothe two solder supply ports 21 of the lead frame 5, respectively. Theplate solder 31 is obtained by deforming plate-shaped solid solder usinga mold or the like, to thereby forming the protruding parts 32.

The lead frame 5 is arranged such that the protruding parts 32 of theplate solder 31 are inserted into the respective corresponding soldersupply ports 21 of the lead frame 5. In the present preferredembodiment, except for the use of the plate solder 31 in place of thesolder block 4, the chip 1 and the lead frame 5 are joined to each otherin the manner similar to the first preferred embodiment.

In the present preferred embodiment, similarly to the first preferredembodiment described above, the protruding parts 32 of the plate solder31 placed on the chip 1 are inserted into the solder supply ports 21 ofthe lead frame 5, whereby the chip 1 and the lead frame 5 aretentatively assembled. Accordingly, similarly to the first preferredembodiment, the effect of stably joining the chip 1 and the lead frame 5to each other can be achieved.

Further, in the present preferred embodiment, similarly to the firstpreferred embodiment, before the chip 1 and the lead frame 5 are fedinto the reflow oven, the plate solder 31 is supplied between the chip 1and the lead frame 5. This achieves the effect similar to that of thefirst preferred embodiment in that the joining processing cansimultaneously be carried out at a plurality of portions without beinginfluenced by the supply time restriction on the solder in the reflowoven.

Still further, being different from the solder block 4 used in the firstpreferred embodiment, the plate solder 31 used in the present preferredembodiment can be manufactured by deformation using a simple apparatuswhose space required for installation is small. Accordingly, the entirejoining apparatus including the manufacturing apparatus of the platesolder 31 can be minimized.

In the present preferred embodiment, while the plate solder 31 havingthe protruding parts 32 is manufactured by deforming the plate solder soas to form the protruding parts 32, the method for manufacturing theplate solder 31 having the protruding parts 32 is not limited thereto.For example, the plate solder 31 having the protruding parts 32 may bemanufactured by placing paste-like solder on the plate solder andthereby forming the protruding parts 32, without deforming the platesolder. Use of the plate solder 31 provided with the protruding parts 32formed in this manner can achieve the effect similar to that achieved bythe present preferred embodiment.

Third Preferred Embodiment

FIG. 5 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a third preferredembodiment of the present invention. Since the structure in thetentatively assembled state according to the present preferredembodiment is similar to the structure in the tentatively assembledstate according to the first preferred embodiment described above, adescription will be given of the different parts, and the correspondingparts are denoted by identical reference symbols and the commondescription will not be repeated.

In the present preferred embodiment, in place of the solder block 4according to the first preferred embodiment, solder 41 that ispreviously soldered to the chip 1 is used. The chip 1 is tentativelyassembled as a soldered chip 42 to which the solder 41 is previouslysoldered. The lead frame 5 is tentatively assembled by being arrangedsuch that the solder 41 of the soldered chip 42 is exposed at the soldersupply ports 21.

FIG. 6 is a flowchart showing the processing procedure in the joiningmethod according to the third preferred embodiment of the presentinvention. When materials and tools used in the joining method accordingto the present preferred embodiment, such as the chip 1, the heatspreader 2, the dedicated jig 3, the solder 41, the lead frame 5 and thelike shown in FIG. 5, are prepared, the processing starts and proceedsto Step b1.

In Step b1, after the molten solder 41 is supplied to the chip 1, thesolder 41 is solidified to thereby manufacture the soldered chip 42. Inthis manner, the soldered chip 42 to which the solid solder 41 is bondedis obtained. The step of Step b1 corresponds to the bonding step. InStep b2, the chip 1 having been soldered in Step b 1, i.e., the solderedchip 42, is assembled into the dedicated jig 3.

In Step b3, the lead frame 5 is placed such that the solder 41 of thesoldered chip 42 is exposed at the solder supply ports 21, whereby thechip 1 and the lead frame 5 are tentatively assembled. The step of Stepb3 corresponds to the tentatively assembling step. In Step b4, thetentatively assembled chip 1 and lead frame 5 are fed into the reflowoven to carry out soldering. The step of Step b4 corresponds to thejoining step.

As described above, in the present preferred embodiment, similarly tothe first preferred embodiment described above, the solder 41 issupplied between the chip 1 and the lead frame 5 before the chip 1 andthe lead frame 5 are fed into the reflow oven. This achieves the effectsimilar to that of the first preferred embodiment in that the joiningprocessing can simultaneously be carried out at a plurality of portionswithout being influenced by the supply time restriction on the solder inthe reflow oven.

Still further, since the soldered chip 42 is used in the presentpreferred embodiment, being different from the first and secondpreferred embodiments, it does not involve the trouble of inserting theprotruding parts 11 of the solder block 4 or the protruding parts 32 ofthe plate solder 31 into the solder supply ports 21 of the lead frame 5.Accordingly, as compared with the first and second preferredembodiments, the chip 1 and the lead frame 5 can be joined to each othermore easily.

FIG. 7 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a modification of thethird preferred embodiment of the present invention. In the modificationof the third preferred embodiment, soldering may previously be carriedout to the lead frame 50 instead of the chip 1. For example, as shown inFIG. 7, a soldered lead frame 52 in which solder 51 is previouslysoldered to the chip 1 may be used. In the present modification, exceptfor the use of the soldered lead frame 52 shown in FIG. 7 in place ofthe soldered chip 42 shown in FIG. 5 described above, joining can becarried out in the similar manner as in the third preferred embodiment.Also in the present modification, the effect similar to that achieved bythe third preferred embodiment can be achieved.

Fourth Preferred Embodiment

FIG. 8 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a fourth preferredembodiment of the present invention. Since the structure of thetentatively assembled state according to the present preferredembodiment is similar to the structure in the tentatively assembledstate according to the first preferred embodiment described above, adescription will be given of the different parts, and the correspondingparts are denoted by identical reference symbols and the commondescription will not be repeated.

In the present preferred embodiment, in place of the solder block 4according to the first preferred embodiment, a metal plate plated withsolder (which hereinafter may be referred to as the “solder-plated metalplate”) 62 is used. In the solder-plated metal plate 62, on the surfaceof a metal plate 60 serving as the base material, a solder-plating layer61 is formed by solder plating. In other words, the solder-plated metalplate 62 is structured to include the metal plate 60 and thesolder-plating layer 61. The solder-plated metal plate 62 corresponds tothe joining material, and the solder-plating layer 61 corresponds to theplating layer.

In the present preferred embodiment, except for the use of thesolder-plated metal plate 62 in place of the solder block 4, joining ofthe chip 1 and the lead frame 5 is carried out in the similar manner asin the first preferred embodiment. When the chip 1 and the lead frame 5are tentatively assembled, the solder-plated metal plate 62 is arrangedsuch that the solder-plating layer 61 is brought into contact with thechip 1 and the lead frame 5.

As described above, in the present preferred embodiment, similarly tothe first preferred embodiment described above, the solder-plated metalplate 62 is supplied between the chip 1 and the lead frame 5 before thechip 1 and the lead frame 5 are fed into the reflow oven. This achievesthe effect similar to that of the first preferred embodiment in that thejoining processing can simultaneously be carried out at a plurality ofportions without being influenced by the supply time restriction on thesolder in the reflow oven.

Still further, in the present preferred embodiment, the solder is usedonly for the solder-plating layer 61 on the surface of the solder-platedmetal plate 62. Therefore, the amount of the solder being used can besaved. Accordingly, a reduction in costs required for joining the chip 1and the lead frame 5 to each other can be achieved.

Though the metal plate 60 that is plated with solder is used as ajoining material in the present preferred embodiment, without beinglimited thereto, the metal plate 60 that is plated with a joining rawmaterial other than solder may be used. It suffices that the joining rawmaterial serves to join the chip 1, the lead frame 5, and the metalplate 60 to each other. For example, the metal plate 60, which isobtained by plating with a brazing material, or the metal plate 60,which is obtained by plating with a metal or an alloy having a lowermelting point than those of the materials of the chip 1, the lead frame5 and the metal plate 60, may be used as the joining material.

That is, a joining material including, on the surface of the metal plate60, a plating layer of a joining raw material other than solder in placeof the solder-plating layer 61 may be used. For example, a joiningmaterial including a layer plated with a brazing material or a layerplated with a metal or an alloy having a lower melting point than thoseof the materials of the chip 1, the lead frame 5 and the metal plate 60may be used. In the cases where such joining materials are employed, theeffect similarly to that in the present preferred embodiment can beachieved.

Fifth Preferred Embodiment

FIG. 9 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a fifth preferredembodiment of the present invention. Since the structure in thetentatively assembled state according to the present preferredembodiment is similar to the structure in the tentatively assembledstate according to the first preferred embodiment described above, adescription will be given of the different parts, and the correspondingparts are denoted by identical reference symbols and the commondescription will not be repeated.

In the present preferred embodiment, solid solder 70 is used in place ofthe solder block 4 according to the first preferred embodiment. Thesolid solder 70 is in a substantially cylindrical shape. In thefollowing, the solid solder 70 may be referred to as the “columnarsolder 70”. The solid solder 70 is made of solid state solder. The solidsolder 70 is previously manufactured in the similar method as that forthe solder block 4 according to the first preferred embodiment describedabove and used.

The solid solder 70 is in an oblate ellipsoid shape. The solid solder 70is inserted in the solder supply ports 21 of the lead frame 5 such thatits long axis direction agrees with the thickness direction of the chip1 and the lead frame 5. Specifically, the solid solder 70 is arranged soas to be inserted into the solder supply ports 21.

FIG. 10 is a flowchart showing the processing procedure in the joiningmethod according to the fifth preferred embodiment of the presentinvention. When materials and tools used in the joining method accordingto the present preferred embodiment, such as the chip 1, the heatspreader 2, the dedicated jig 3, the solid solder 70, the lead frame 5and the like shown in FIG. 9, are prepared, the processing starts andproceeds to Step c1.

In Step cl, similarly to the first preferred embodiment described above,after the chip 1 is soldered to the heat spreader 2, the heat spreader 2to which the chip 1 is soldered is assembled into the dedicated jig 3.

In Step c2, being different from the first preferred embodiment, thechip 1 and the lead frame 5 are tentatively assembled by placing thelead frame 5 above the chip 1 without having the solder block 4interposed therebetween. The lead frame 5 is supported by not-shownsupporting means, e.g., a robot arm or a fixing member, and placed abovethe chip 1. The step of Step c2 corresponds to the tentativelyassembling step.

After the tentative assembly, in Step c3, the substantiallycylindrically shaped solid solder 70 is inserted into each of the soldersupply ports 21 of the lead frame 5, and fed into the reflow oven inStep c4. The step of Step c3 corresponds to the supplying step, and thestep of Step c4 corresponds to the joining step.

As described above, in the present preferred embodiment, similarly tothe first preferred embodiment described above, the solder is suppliedby inserting the solid solder 70 into the solder supply ports 21 of thelead frame 5 before the chip 1 and the lead frame 5 are fed into thereflow oven. This achieves the effect similar to that of the firstpreferred embodiment in that the joining processing can simultaneouslybe carried out at a plurality of portions without being influenced bythe supply time restriction on the solder in the reflow oven.

Further, since the solid solder 70 being substantially cylindricallyshaped columnar solder is used in the present preferred embodiment, ascompared to the case where the solder block 4 is used, the supply amountof the solder can be reduced. Accordingly, it is effective in the casewhere the area joined by the joining material such as solder (whichhereinafter may be referred to as the “joining area”) is relativelysmall.

Since the solder supply source employed in the joining method ofconventional technique such as disclosed in Japanese Patent ApplicationLaid-Open No. 2008-182074 described above is associated with variationsattributed to the structure, it is difficult to finely adjust the supplyamount of solder. Accordingly, in the case where solder is discharged ina small amount and applied, such as in the case where a relatively smallchip is soldered, the applied amount will vary, which invites troubles.

Accordingly, what is required is a joining method that can suppressvariations in the supply amount of the joining material to the joiningtarget member such as the chip 1 irrespective of the size of the joiningarea, and that can carry out joining evenly and simultaneously at aplurality of portions even when the joining area is reduced due tominiaturization of the joining target member.

In the present preferred embodiment, as described above, since thesupply amount of the joining material such as solder can be maderelatively small, variations in the supply amount of the joiningmaterial to the joining target member such as the chip 1 can besuppressed irrespective of the size of the joining area. Further, evenwhen the joining area is reduced due to miniaturization of the joiningtarget member, joining can be carried out evenly and simultaneously at aplurality of portions.

FIG. 11 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a modification of thefifth preferred embodiment of the present invention. A solder wire 71being a cylindrical solid solder that is shown in FIG. 11 may beemployed in place of the solid solder 70 being a substantiallycylindrical shape columnar solder that is shown in FIG. 9 describedabove in the modification of the fifth embodiment of the presentinvention. Also in the case where the solder wire 71 is used as in thepresent modification, the effect similar to that achieved by the fifthpreferred embodiment can be achieved. Further, when the solder wire 71is used, the involved work is only cutting of the solder. Therefore, ascompared to the case where the substantially cylindrically shapedcolumnar solder 70 is used in the fifth preferred embodiment, the workcan be carried out in an easier manner. The solder wire 71 correspondsto the wire-like joining material.

Sixth Preferred Embodiment

FIG. 12 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a sixth preferredembodiment of the present invention. FIG. 13 is a plan view showing thestructure in the tentatively assembled state in the joining methodaccording to the sixth preferred embodiment of the present invention.FIG. 12 corresponds to a cross-sectional view taken alongcross-sectional line S12-S12 in FIG. 13. Since the structure in thetentatively assembled state according to the present preferredembodiment is similar to the structure in the tentatively assembledstate according to the fifth preferred embodiment described above, adescription will be given of the different parts, and the correspondingparts are denoted by identical reference symbols and the commondescription will not be repeated.

In the present preferred embodiment, a lead frame 80 provided withsolder supply ports (which hereinafter may be referred to as the “endsolder supply ports”) 81 at positions opposing to the end of the chip 1is used. The lead frame 80 according to the present preferred embodimentis structured to include the lead frame 5 according to the fifthpreferred embodiment and the additional end solder supply ports 81. Inthe present preferred embodiment, four end solder supply ports 81 areformed at the lead frame 80. In the following, the solder supply ports21 formed as being aligned with the slit 22 similarly to the soldersupply ports 21 formed at the lead frame 5 according to the fifthpreferred embodiment may be referred to as the “inner solder supplyports 21”.

Similarly to the inner solder supply ports 21, the end solder supplyports 81 penetrate through the lead frame 80 in the thickness direction.

Similarly to the inner solder supply ports 21, the end solder supplyports 81 are each formed in an oval shape as seen from the other side inthe thickness direction of the lead frame 80. The end solder supplyports 81 are formed two in number on each of the opposite sides in theshorter side direction of the slit 22, with reference to the slit 22.One end solder supply port 81, one inner solder supply port 21, and theother one end solder supply port 81 are aligned along the longitudinaldirection of the slit 22. Each of the end solder supply port 81 isformed at a position opposing to the end of the chip 1.

The joining method according to the present preferred embodiment issimilarly performed as the joining method according to the fifthpreferred embodiment described above. Specifically, in Step c1 shown inFIG. 10 described above, the chip 1 is soldered to the heat spreader 2,and assembled into the dedicated jig 3. In Step c2, similarly to thefifth preferred embodiment, the chip 1 and the lead frame 80 aretentatively assembled.

Thereafter, in Step c3, similarly to the fifth preferred embodiment, thesolid solder 70 is inserted into each of the solder supply ports 21 and81 of the lead frame 80. Subsequently, in Step c4, the tentativelyassembled chip 1 and the lead frame 80 are fed into the reflow oven,whereby the solid solder 70 inserted into the solder supply ports 21 and81 are heated and melted. Thereafter, the tentatively assembled chip 1and the lead frame 80 are taken out from the reflow oven and cooled, sothat the molten solid solder 70 is solidified. Thus, the chip 1 and thelead frame 80 are joined to each other.

As described above, in the present preferred embodiment, similarly tothe first and fifth preferred embodiments described above, the solder issupplied by inserting the solid solder 70 into the solder supply ports21 and 81 of the lead frame 80 before the chip 1 and the lead frame 80are fed into the reflow oven. This achieves the effect similar to thatof the first and fifth preferred embodiments in that the joiningprocessing can simultaneously be carried out at a plurality of portionswithout being influenced by the supply time restriction on the solder inthe reflow oven.

Further, the lead frame 80 according to the present preferred embodimentis provided with end solder supply ports 81 at positions opposing to theends of the chip 1. This makes it possible to directly supply the solderto the ends of the chip 1, whereby insufficient wetting of the solder atthe ends of the chip 1 can be prevented.

Though the solid solder 70 in a specific shape is used in theabove-described present preferred embodiment similarly to the fifthpreferred embodiment described above, without being limited thereto, thesolder in other shape such as the cut solder wire 71 described above andshown in FIG. 11 may also be used. In this case also, the effect similarto that achieved by the present preferred embodiment can be achieved.

Seventh Preferred Embodiment

FIG. 14 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a seventh preferredembodiment of the present invention. In the present preferredembodiment, joining is carried out by supplying molten solder in thereflow oven, in place of use of the solder block 4 in the firstpreferred embodiment described above. To this end, in the presentpreferred embodiment, being different from the first preferredembodiment, a non-joining portion that is the portion not to be joinedis covered by a mask 6 made of a material that does not join with thesolder, and the molten solder is supplied from the opening portion 6 aof the mask 6.

FIG. 15 is a flowchart showing the processing procedure in a joiningmethod according to a seventh preferred embodiment of the presentinvention. When materials and tools used in the joining method accordingto the present preferred embodiment, such as the chip 1, the heatspreader 2, the dedicated jig 3, the lead frame 5, the mask 6 and thelike shown in FIG. 14, are prepared, the processing starts and proceedsto Step d1.

In Step d1, similarly to the first preferred embodiment described above,after the chip 1 is soldered to the heat spreader 2, the heat spreader 2to which the chip 1 is soldered is assembled into the dedicated jig 3.

In Step d2, the non-joining portion of the chip 1 is covered by the mask6. In Step d3, the lead frame 5 is placed on the chip 1 having the mask6 interposed therebetween, and the chip 1 and the lead frame 5 aretentatively assembled. The lead frame 5 is supported by not-shownsupporting means, e.g., a robot arm or a fixing member, and placed onthe chip 1.

After the tentative assembly, in Step d4, the tentatively assembled chip1 and lead frame 5 are fed into the reflow oven. In Step d5, in thereflow oven, from a plurality of portions, specifically, from the twosolder supply ports 21 of the lead frame 5, the molten solder issupplied simultaneously by being poured into the opening portion 6 a ofthe mask 6.

Thereafter, the tentatively assembled chip 1 and lead frame 5 are takenout from the reflow oven and cooled, so that the molten soldersolidifies. Thus, the chip 1 and the lead frame 5 are joined to eachother. Thereafter, the mask 6 is peeled off.

As described above, in the present preferred embodiment, since themolten solder is supplied in the state where the non-joining portion iscovered by the mask 6, the joining processing can simultaneously becarried out at a plurality of portions without being influenced by thesupply time restriction on the solder in the reflow oven. In otherwords, the joining processing can be carried out simultaneously at aplurality of portions, just by adjusting the shape of the mask 6.Accordingly, since it is not necessary to perform works to the chip 1 orthe lead frame 5 for realizing the joining processing, the joiningprocessing at a plurality of portions can easily be carried out evenwhen the joining portions are relatively great in number.

The material of the mask 6 may be any material that does not join withsolder, e.g., stainless steel. By forming the mask 6 with a materialthat does not join with solder, the effect described above can beachieved with the mask 6 of various shapes.

Eighth Preferred Embodiment

FIG. 16 is a cross-sectional view showing the structure in a soldersupplying state in the reflow oven in a joining method according to aneighth preferred embodiment of the present invention. Since thestructure of the present preferred embodiment is similar to thestructure of the first preferred embodiment described above, adescription will be given of the different parts, and the correspondingparts are denoted by identical reference symbols and the commondescription will not be repeated.

In the present preferred embodiment, the lead frames 5 are respectivelyjoined to a plurality of the chips 1. In the present preferredembodiment, being different from the first preferred embodimentdescribed above, without assembling the solder block 4, the chips 1 andrespective corresponding lead frames 5 are tentatively assembled, andfed into the reflow oven. Then, in the reflow oven, molten solder 90 issimultaneously supplied to the chips 1 from a plurality of solder supplysources 7.

FIG. 17 is a flowchart showing the processing procedure in a joiningmethod according to the eighth preferred embodiment of the presentinvention. When materials and tools used in the joining method accordingto the present preferred embodiment, such as the chips 1, the heatspreader 2, the dedicated jig 3, the lead frames 5 and the like shown inFIG. 16 are prepared, the processing starts and proceeds to Step e1.

In Step e1, similarly to the first preferred embodiment described above,after the chips 1 are soldered to the heat spreader 2, the heat spreader2 to which the chips 1 are soldered is assembled into the dedicated jig3.

In Step e2, the lead frames 5 are placed above the chips 1 withouthaving any solder block 4 interposed therebetween, and the chips 1 andthe lead frames 5 are tentatively assembled. The lead frames 5 aresupported by not-shown supporting means, for example by a robot arm or afixing member, and placed above the chips 1.

After the tentative assembly, in Step e3, the tentatively assembledchips 1 and lead frames 5 are fed into the reflow oven. In Step e4, inthe reflow oven, simultaneously from a plurality of solder supplysources 7, the molten solder 90 is supplied. Thereafter, the tentativelyassembled chips 1 and lead frames 5 are taken out from the reflow ovenand cooled, so that the molten solder 90 solidifies. Thus, the chips 1and the lead frames 5 are joined to each other.

As described above, in the present preferred embodiment, since themolten solder 90 is supplied simultaneously from a plurality of soldersupply sources 7 to the chips 1, the joining processing cansimultaneously be carried out at a plurality of portions without beinginfluenced by the supply time restriction on the solder in the reflowoven.

Ninth Preferred Embodiment

FIG. 18 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a ninth preferredembodiment of the present invention. Since the structure of the presentpreferred embodiment described above is similar to the structure of thefirst preferred embodiment, a description will be given of the differentparts, and the corresponding parts are denoted by identical referencesymbols and the common description will not be repeated.

In the present preferred embodiment, the solder block 4 being solidsolder is supplied between the chip 1 and the lead frame 5 similarly tothe first preferred embodiment described above, and additionally, afterthe tentative assembly, solder balls 91 are supplied from the soldersupply ports 21, and they are fed into the reflow oven. The solder balls91 each correspond to the spherical joining material.

In the present preferred embodiment, the effect similar to that achievedby the first preferred embodiment described above can be achieved.Further, in the present preferred embodiment, by supplying the solderballs 91, the supply amount of solder is increased as compared to thefirst preferred embodiment. Accordingly, the joining method of thepresent preferred embodiment is particularly effective when the joiningarea is relatively great.

FIG. 19 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a modification of theninth preferred embodiment of the present invention. As shown in FIG.19, in the modification of the ninth preferred embodiment, in place ofthe solder balls 91, solder wires 92 having been cut may be used. Thesolder wires 92 each correspond to the wire-like joining material.Further, in place of the solder block 4, the plate solder 31 accordingto the second preferred embodiment may be used. In the cases where theyare used also, the effect similar to that achieved by the ninthpreferred embodiment can be achieved.

Tenth Preferred Embodiment

FIG. 20 is a cross-sectional view showing the structure in a tentativelyassembled state in a joining method according to a tenth preferredembodiment of the present invention. Since the structure in thetentatively assembled state of the present preferred embodiment issimilar to the structure in the tentatively assembled state according tothe third preferred embodiment described above, a description will begiven of the different parts, and the corresponding parts are denoted byidentical reference symbols and the common description will not berepeated.

In the present preferred embodiment, the soldered chip 42 is usedsimilarly to the third preferred embodiment, and additionally, after thetentative assembly, the solder balls 91 are supplied from the soldersupply ports 21 and they are fed into the reflow oven similarly to theninth preferred embodiment. The solder balls 91 each correspond to thespherical joining material.

According to the present preferred embodiment, the effect that issimilar to that achieved by the third preferred embodiment describedabove can be achieved. Further, similarly to the ninth preferredembodiment, by supplying the solder balls 91, the supply amount ofsolder is increased as compared to the third preferred embodiment.Accordingly, the joining method according to the present preferredembodiment is particularly effective when the joining area is relativelygreat.

Though it is different from the present preferred embodiment, use of thelead frame 80 with additional solder supply ports 81 as in the sixthpreferred embodiment described above can achieve the similar effect.

The joining methods according to the first to tenth preferredembodiments described above can be used in combination as appropriate.For example, by combining the joining method according to the firstpreferred embodiment and the joining method according to the fourthpreferred embodiment, it becomes possible to join the joining targetmembers at the accurate position while suppressing the use amount of thesolder.

A semiconductor device manufacturing method according to the otherembodiment of the present invention includes a step of joining thesemiconductor chip 1 and the lead frame 5 to each other using one of thejoining methods according to the first to tenth preferred embodimentsdescribed above. The semiconductor chip 1 includes a semiconductorelement. The lead frame 5 includes a lead wire connected to thesemiconductor element to each other. Joining the semiconductor chip 1and the lead frame 5 specifically means joining the semiconductorelement of the semiconductor chip 1 and the lead wire of the lead frame5 to each other.

As described above, according to the joining methods of the first to thetenth preferred embodiments, the joining processing can simultaneouslybe carried out at a plurality of portions without being influenced bythe supply time restriction on the joining material. By joining thesemiconductor chip 1 and the lead frame 5 to each other through use ofsuch joining methods, the number of semiconductor chips 1 mounted on asemiconductor device can be increased.

While the invention has been shown and described in detail, theforegoing description is in all aspects illustrative and notrestrictive. It is therefore understood that numerous modifications andvariations can be devised without departing from the scope of theinvention.

1-13. (canceled)
 14. A joining method for joining two joining targetmembers, comprising: a tentatively assembling step of tentativelyassembling said two joining target members to oppose to each other withan interval between said two joining target members; and a joining stepof joining said two joining target members by supplying a molten joiningmaterial using supplying means to a space formed by said two joiningtarget members and thereafter solidifying the molten joining material,wherein said supplying means is structured to be capable ofsimultaneously supplying said joining material to a plurality ofportions.
 15. The joining method according to claim 14, wherein saidsupplying means includes: a mask that exposes a portion to be joined ofeach of said two joining target members and that covers other portion;and a supply source that supplies said molten joining material, whereinsaid tentatively assembling step is a step of tentatively assemblingsaid two joining target members by having said mask interposed betweensaid two joining target members, and in said joining step, said moltenjoining material is supplied from said supply source to said portion tobe joined being exposed outside said mask.
 16. The joining methodaccording to claim 14, wherein said supplying means includes a pluralityof supply sources that each supply said molten joining material, whereinin said joining step, said plurality of supply sources each supply saidmolten joining material into a space formed by said two joining targetmembers.
 17. (canceled)